Abstract
For RF-pilot-assisted PDM-CO-OFDM systems, we propose and demonstrate a carrier
recovery method applying a simple moving average filter (MAF) to extract the central
RF-pilot for phase noise compensation. Because only two additions per output sample
would be required to implement such a MAF, its computational complexity is rather simple
compared to any other direct-form finite impulse response (FIR) filter. To handle its
weak side-lobe attenuation, which would cause the spectrally nearby OFDM signal to
interfere with the extracted pilot signal, we further propose using multiple MAFs in
cascade to enhance the side-lobe attenuation. We evaluate the performance of a 16-QAM
and 40-Gbps PDM-CO-OFDM signal, in terms of the bandwidth tolerance, optical signal to
noise ratio (OSNR) tolerance, nonlinear tolerance, linewidth tolerance, and residual
carrier frequency offset (RFO) tolerance, with different filters including the simple
MAF, cascaded MAFs, and the previously-demonstrated multi-stage decimation and
interpolation filter (MDIF). We've found that 1) all the filters exhibit similar
performance to the ideal brick-wall filter in terms of noise and nonlinear tolerances,
2) the MAF1 exhibits the worse tolerances against linewidth and RFO, and 3) the MDIF has
to be carefully designed to enhance its tolerances against both the linewidth and
RFO.
© 2013 IEEE
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